It eventually happens to every new photographer. You’re out in the field. You’re setting up to make a shot, and you see others around you setting up for a shot, only, some of these people have these strange contraptions attached to the front of their lens. It looks like a huge piece of square glass. You sit there. You stare. You wonder. And when you get back home, you Google ‘square things on lens.’ The first time this happened to me, I was set up to shoot some images of Bonsai Rock in Lake Tahoe, California several years back. It’s a rock about a hundred yards offshore that has miniature trees growing on it as a result of the trees roots not being able to penetrate the rock, effectively stunting their growth. Anyhow, I had my positioning, tripod locked down, and others began to show up and set up, and a few of them set up with these aforementioned chunks of glass. I had to know what they were, so I asked the photographer next to me, who kindly explained what they do and the effect they give. They lent me one, showed me a crude way of using it by holding it front of my lens (they had special holders for theirs) and I was immediately blown away. Everything became so clear to me. All those crazy images I see on 500px.com and around the web with milky smooth water and skye and clouds…I get it now.

The one they let me use was a Graduated Neutral Density filter, and I explain what that does below, along with the 5 most popular photography filters used by photographers in the field.

1. UV Filter - This filter does absolutely nothing, yet, it is by far the most popular. Huh? Well, because it does nothing to the image itself, many photographers will have them on their lens to protect the glass. While a lens can be in the thousands of dollars, a basic UV filter can be under 30, so it’s a minimal investment to protect your gear. Plus, it does actually help a little bit in minimizing haze and glare. These come in circular shape and screw onto the front of your lens so you forget it’s even there. They’re sold by the size of the lens, which is demonstrated on the barrel of the lens following the ø symbol. For example, in this image, you’ll see ø67, so the size of filter I’d shop for is 67mm.

2. Polarizer - Essentially this one is most commonly used to darken and saturate skies, as well as reduce reflections in reflective surfaces such as water and glass. They can also be extremely effective in making colors pop in overcast conditions. Polarizers, like UV filters, also usually comes in the circular screw-on format. Once you screw it on, you can turn it and see the effects immediately through your viewfinder or LCD panel. On sunny days, they work best the closer you are to a 90 degree angle from the sun (when the sun is directly overhead or to either side of you).

3. Graduated Neutral Density (Grad ND) - It’s basically a piece of glass that gradually moves from no tint to a dark tint, with a discernible line along the middle. What this does is it allows the proper amount of light through the part of the glass where there is no tint, to letting less light in the part of the glass with the tint. Essentially, this makes it so that whatever is under the tint is underexposed, allowing you to increase your exposure time to still get a proper exposure for the scene. Basically, you can decrease your shutter speed, allowing for a longer exposure in the lighter areas without overexposing the full image. For example, in the shot of Bonsai Rock, the sky was much brighter than the water and the foreground in my image, so it would have been impossible to get a good exposure of the entire scene. So I wanted to be able to allow less light into the bright areas while I expose for the darker areas. By placing the filter so that the dark tint is on the top half (or horizon) of my scene and darkening my sky, I am able to get a proper exposure preserving detail in both halves of the scene. These filters typically need a filter holder as explained below.

4. Neutral Density (ND) - This is almost the same as the graduated neutral density filter described above. The only difference is that on a regular neutral density filter, the entire glass is one tint. They come in various degrees of tints, called stops. This is in relations to your f-stop, so a 3-stop ND filter will allow you to expose for 3 additional f-stops to get a proper exposure, a 6-stop ND will allow you to expose for 6 additional f-stops, and so on (which also applies for the Graduated Neutral Density filters). Neutral Density filters are best used on very bright days when you want to accomplish a long-exposure. This way, the filter darkens the glass, creating the opportunity to keep your shutter open for a longer exposure. Neutral Density filters also usually require a filter holder.

5. Infrared - Madness! That’s what these create. Essentially, what Infrared filters do is block infrared light while letting through visible light. By blocking out certain spectrums of light, IR filters allow us to view spectrums of light that are normally lost to the human eye. Using an IR-transmitting filter will result in almost monochromatic surreal images with colors that we don’t normally see to the naked eye. The detail the provide can be insane! Click here for a few examples. (Edit: As pointed out by Google Plus user Jonathan Allen, "most cameras have built in infrared filters. Removing the infrared filter is what produces the effects in the photos you linked to under the infrared filter." He is correct, to a degree. There are actually two things going on here. There is an IR-blocking filter, and an IR-transmitting filter. the IR-blocking filter is what the camera is equipped with in order to block the infrared spectrum from coming to the sensor and making your images unnatural looking. The IR-transmitting filter is what allows the infrared spectrum to hit the sensor, giving that surreal effect. It's the same effect you'd get if you had the IR-filter that is built into the camera removed).

So there’s the basic breakdown of five of the more popular filters. The other element here is the filter holder and that depends on your lens. Certain ones are made for wide angle lenses, others are made for more standard focal length lenses. They basically screw onto the front of your lens and then the filter slips into the grooves provided.

If you're on a budget and want to affordably play around a bit before committing to the higher-end brands and options, Cokin and Tiffen are worth checking out.

And recently, I've been introduced to Haida, and got myself a 10-stop Neutral Density filter. They're designed to compete with Lee's Big Stopper and THEY DO THE TRICK!!! Here's one, shot in Hawaii, literally at high noon, and I was able to get this gorgeous 30-second exposure shown here on the right.

Try to stay away from the plastic filters and stick to the glass ones – you WILL notice the difference in quality.

While I learned the lesson of the power of the filter in the field, that wasn’t the only lesson I learned on that shoot. The other was that no matter how warm the weather, do NOT ever ever EVER wear flip-flops, especially when you have to scale a small cliff to get into position. I tore the sucker on the way down and climbing with photo gear half-bare-foot along a rocky lakeside isn’t…eh…comfortable.

Regardless, my resulting shot was worth it (or at least I thought so…).